Bring plenty of water to a boil in a large pot. Unlike pasta, do not add salt to the cooking water.

Add the dried soba noodles to the boiling water, spreading them around the pot in a circular pattern to keep them separate.

Cook the soba noodles according to the package instructions. Stir occasionally so they don’t stick together.

The noodles are ready when just tender; do not overcook. Before draining, reserve a large bowl of the cooking water called "sobayu" to mix with any leftover dipping sauce at the end of the meal.

Drain the soba noodles in a colander and rinse under cold running water to remove excess starch. This is a very important step to prevent the noodles from sticking together.

Shake the colander to drain completely. Transfer the noodles to a large bowl of ice water. Chill for 30 seconds, drain well, and set aside.

To serve, place sieves or bamboo mats on individual plates (to catch any dripping water). Arrange a portion of soba on each mat and top with shredded nori.

Use about a 1:3 ratio of mentsuyu to water—for example, combine 45 ml mentsuyu with 135 ml ice water—and taste to adjust. If it’s too salty, add more water; if it’s too diluted, add more mentsuyu.

Place the green onion and wasabi in small individual dishes and serve alongside the soba with small bowls for dipping.